MrFancypants Posted January 5, 2007 Share Posted January 5, 2007 Upon closer inspection of my fuel filter, I realized that the electric fuel pump by the gas tank is disconnected. The lines are all still connected (tank-filter-pump-line to engine). Im thinking I should just pull the fuel pump entirely and connect the outlet of the fuel filter directly to the fuel line. I have read that the electric pump is there to avoid vapor lock issues. The car seems to run fine with the pump disconnected, so can somebody explain what Im missing out on? The old school gas cap doesnt make an air tight fit. It has a small hole in it -- should it? The evap line in the engine bay was also disconnected from the air cleaner and crankcase. Could this play into vapor lock? Thanks, - Greg - Quote Link to comment Share on other sites More sharing options...
BillZ260 Posted January 5, 2007 Share Posted January 5, 2007 you are right about the electric pump, i'd say if your car has always ran fine but had the 2nd pump unpluged then you could remove it. As far as the gas cap goes, I'm not sure. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted January 5, 2007 Share Posted January 5, 2007 Well I am doing the reverse of this... My 260Z has L24 flattops raising the compression a bit so it is realy sensitive to the gas that it gets. I have my rear fuel pump hooked up to new wiring and a switch. I would drive the car all day when it was off and not really tell a difference. When I flip a switch though the car runs smoother and stronger. It is enough difference that my butt-dyno can tell. If you have run the fuel pump for testing and just ran a tube back into the tank you can see how MUCH fuel it can move. I was very suprised when I tested it and it SHOT gas!! I am going to remove my mechancal fuel pump and just run the electric because I think the mechanical one puts restriction on the system more tha it helps. With the car off and the electric pump running you can hear fuel shooting out the return line into the tank... Plus you can have an anti-theft with just the electric pump and a hidden switch hooked to ignition power. Quote Link to comment Share on other sites More sharing options...
MrFancypants Posted January 5, 2007 Author Share Posted January 5, 2007 Since I'll be going EFI eventually, I dont want to replace the stock electric fuel pump. I suppose I should check to see if it actually broke or if the nimrod just cut the wires for fun. I just cant see why you'd leave it in there if it's not on -- you'd think it would restrict flow. Really curious about the gas cap now... I looked closer at it and the hole looks like it may be drilled. Why on earth would someone do that? - Greg - Quote Link to comment Share on other sites More sharing options...
260pos Posted January 6, 2007 Share Posted January 6, 2007 EFI requires a higher pressure than carburetors, the stock pump won’t cut it, and so it really doesn’t matter whether you leave it or pull it. The pump it only there to help the mechanical pump out, as 260’s don’t have a fuel return to prevent vapor lock. Quote Link to comment Share on other sites More sharing options...
260pos Posted January 6, 2007 Share Posted January 6, 2007 Oh! The reason for the hole is to vent the cap (tank) after the evaporative emission canister was removed and pluged. Quote Link to comment Share on other sites More sharing options...
MrFancypants Posted January 6, 2007 Author Share Posted January 6, 2007 You know... the previous owner must have added a fuel return then. There is definitely a line returning to the tank off the "fuel rail". Does the stock 260Z gas tank not have a return line on it? Now Im wondering if the gas tank was replaced. There are 3 fuel hardlines along the frame - my assumption is feed, return, and vent. There's definitely a fuel smell coming out of the vent line in the engine bay. If I plumb this back into the intake as it was intended, I should be able to reseal the gas cap, right? - Greg - Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted January 6, 2007 Share Posted January 6, 2007 260Zs DO have a return line and also have a line that went to a charcoal canister on the passenger side near the radiator. Quote Link to comment Share on other sites More sharing options...
MrFancypants Posted January 6, 2007 Author Share Posted January 6, 2007 260Zs DO have a return line and also have a line that went to a charcoal canister on the passenger side near the radiator. Ok things are looking clearer now. The charcoal canister was indeed removed because the line is on the passenger side but open. The evap system appears much more advanced than the 240Z system. Since I dont have a carbon canister, I think my next step is to replace the fuel cap with a sealing one and plumb the vapor line into the intake. Probably need to find a vacuum valve too and connect in the crankcase like the 240 setup. I also read up on the electric fuel pump in my FSM. Didnt realize it would have such a detailed section on it. It is in fact serviceable and has an internal filter. Guess that's my next step. - Greg - Quote Link to comment Share on other sites More sharing options...
260pos Posted January 6, 2007 Share Posted January 6, 2007 260Zs DO have a return line and also have a line that went to a charcoal canister on the passenger side near the radiator. All right, You got me there! I want and dissected the (probably asbestos ) wrap off my fuel rail, and sure enough! It loops back… Doh! Thanks for the clarification. Quote Link to comment Share on other sites More sharing options...
MrFancypants Posted May 13, 2007 Author Share Posted May 13, 2007 Hate to resurrect this one, but why start a new thread So I revealed the "vapor separator" today. Seems kind of silly to have all those hoses routed into the cabin that can just deteriorate and leak fumes. I was thinking of removing the vapor separator entirely, joining the large tank vent hose to the fuel filler neck and joining the small tank vent hose directly to the fuel vent hard line. Then connect the vent line at the front of the car to the crankcase/air cleaner through a valve. I have a EVAP purge control valve from my wrecked G20 that should do the trick. Is the vapor separator all that necessary? The way I look at it, my fuel vent wasnt even connected so the vapor separator was basically doing nothing. Whats the benefit of a charcoal canister? Can you plumb the fuel vapors into the intake without a canister or will you end up sucking fuel right through the vent line? - Greg - Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 15, 2007 Share Posted May 15, 2007 Don't vent the carbon cannister line to the manifold! Vent it to the air cleaner, or stick one of those small K&N Keychain filters on the end. If you attach the vapor line to the manifold, it will SUCK the tank in---there is enough vacuum during deceleration that if all your other hoses are properly sealed, you will crush the gas tank like a tin can! Just vent it to atmosphere with a small filter to let air out when you fill it, and air back into the tank when you are dsriving and sucking gas out. the Benefit of the carbon cannister is that it's filled with about a milloin square feet of activated carbon surface area to adsprb fuel vapors, and then liberates them during startup and run of the engine without you smelling all that raw gas around the car after a hot shutdown. As above, don't vent it to the manfiold. simply vent it to the air cleaner. Quote Link to comment Share on other sites More sharing options...
MrFancypants Posted May 15, 2007 Author Share Posted May 15, 2007 Ok so I got rid of the vapor separator as described, only to find a nice big puddle of gas on my garage floor a few hours later. God what a stench. Turns out I had the return line open and in the high heat of the day (~104F on Sunday bleah) the gas just expanded right out the fuel return. Stupid me, yeah I know. This made me notice that, since my car has a L28 swap and round top carbs thanks to a previous owner, the fuel return line does nothing. In fact, the return was connected to what should be the EVAP purge line to the fuel rail (small line with pinhole above mech fuel pump). Where is the return line supposed to go on the L24, or is there even one? Was there no EVAP purge line on the L24 rail and thats actually the fuel return? The size of that line is tiny (maybe 3/16") compared to the fuel return (5/16"). Should I seal off the return or flare up the connection between the return line and the fuel rail? Tony, by "intake" I didnt mean the manifold after the TB, but the filter before the TB. There shouldnt be any vacuum on it. But this begs another question, if I go with the vac operated valve to switch the vapor line between the crankcase and the intake, will there be sufficient release without vacuum. In other words, when the car is off and sitting or I fill the tank, will the vapor line bleed off to the crankcase? Will this eliminate fuel fumes? This is how I was led to believe the 240Z system works in another thread. - Greg - Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted May 15, 2007 Share Posted May 15, 2007 My carbon canister line is just sitting there open...and has done so for the last 3 years... I have gas going in right above the Mechanical fuel pump and the return comes back right above it. The carbon canister is located at the front passenger side of the engine bay on a vertical bracket with a nut welded onto the back. My line is just venting to the atmosphere there. I mounted my air horn compressor to the carbon canister bracket and pinched the vent line closed... Quote Link to comment Share on other sites More sharing options...
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